This book repared by partners of the Sustainable Sanitation Alliance (SuSanA) network is a real eye-opener. It takes a look at some of the methods that have worked well in the past, to guide us in solving the problems of the future. By addressing sanitation as a key element of the urban metabolism, and by linking sanitation with urban planning and neighbouring sectors like solid waste management or waste recycling, it allows for a holistic approach. In the cities of tomorrow, we will need to focus more on recycling energy. A good example being biogas generation from wastewater and sludges. Water will also become an increasingly scarce commodity. Greywater (from showers and sinks) can be treated in urban constructed wetlands or used to water and fertilise urban green spaces. Such examples of productive sanitation systems will form an integral part of infrastructure in sustainable cities.